Study of interfaces chemistry in type-II GaSb/InAs superlattice structures

There is a considerable interest in type-II GaSb/InAs superlattice system due to several modern applications including infrared detectors. In these studies X-ray Photoelectron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) have been used to extensive characterization of the surface and interface of GaSb/InAs superlattice. Application of XPS and SE techniques provide precise information from topmost layers of structure and allow excluding presence of GaAs-type interfaces in GaSb/InAs superlattices. Simultaneously, these results indicate that InSb-type or GaInSb-type interfaces have been detected in the structures studied

Spheroid-plug model as a tool to study tumor development, angiogenesis, and heterogeneity in vivo

Subcutaneous injection of the tumor cell suspension is a simple and commonly used tool for studying tumor development in vivo. However, subcutaneous models poorly resemble tumor complexity due to the fast growth not reflecting the natural course. Here, we describe an application of the new spheroid-plug model to combine the simplicity of subcutaneous injection with improved resemblance to natural tumor progression. Spheroid-plug model relies on in vitro formation of tumor spheroids, followed by injection of single tumor spheroid subcutaneously in Matrigel matrix. In spheroid-plug model, tumors grow slower in comparison to tumors formed by injection of cell suspension as assessed by 3D ultrasonography (USG) and in vivo bioluminescence measurements. The slower tumor growth rate in spheroid-plug model is accompanied by reduced necrosis. The spheroid-plug model ensures increased and more stable vascularization of tumor than classical subcutaneous tumor model as demonstrated by 3D USG Power Doppler examination. Flow cytometry analysis showed that tumors formed from spheroids have enhanced infiltration of endothelial cells as well as hematopoietic and progenitor cells with stem cell phenotype (c-Kit+ and Sca-1+). They also contain more tumor cells expressing cancer stem cell marker CXCR4. Here, we show that spheroid-plug model allows investigating efficiency of anticancer drugs. Treatment of spheroid-plug tumors with known antiangiogenic agent axitinib decreased their size and viability. The antiangiogenic activity of axitinib was higher in spheroid-plug model than in classical model. Our results indicate that spheroid-plug model imitates natural tumor growth and can become a valuable tool for cancer research

Differential inflammatory microRNA and cytokine expression in pulmonary sarcoidosis

Sarcoidosis is a granulomatous disease of unknown etiology. The disease has an important inflammatory and immune component; however, its immunopathogenesis is not completely understood. Recently, the role of microRNAs (miRNAs), the small non-coding RNAs, has attracted attention as both being involved in pathogenesis and serving as disease markers. Accordingly, changes in the expression of some miRNAs have been also associated with different autoimmune pathologies. However, not much is known about the role of miRNAs in sarcoidosis. Therefore, the aim of this study was to compare the level of expression of selected miRNAs in healthy individuals and patients with sarcoidosis. We detected significantly increased level of miR-34a in peripheral blood mononuclear cells isolated from sarcoidosis patients. Moreover, significantly up-regulated levels of interferon (IFN)-γ, IFN-γ inducible protein (IP-10) and vascular endothelial growth factor were detected in sera of patients when compared to healthy subjects. Our results add to a known inflammatory component in sarcoidosis. Changes in the levels of miR-34a may suggest its involvement in the pathology of this disease

Very small embryonic-like stem cells (VSELs) represent a real challenge in stem cell biology : recent pros and cons in the midst of a lively debate

The concept that adult tissue, including bone marrow (BM), contains early-development cells with broader differentiation potential has again been recently challenged. In response, we would like to review the accumulated evidence from several independent laboratories that adult tissues, including BM, harbor a population of very rare stem cells that may cross germ layers in their differentiation potential. Thus, the BM stem cell compartment hierarchy needs to be revisited. These dormant, early-development cells that our group described as very small embryonic-like stem cells (VSELs) most likely overlap with similar populations of stem cells that have been identified in adult tissues by other investigators as the result of various experimental strategies and have been given various names. As reported, murine VSELs have some pluripotent stem cell characteristics. Moreover, they display several epiblast/germline markers that suggest their embryonic origin and developmental deposition in adult BM. Moreover, at the molecular level, changes in expression of parentally imprinted genes (for example, Igf2–H19) and resistance to insulin/insulin-like growth factor signaling (IIS) regulates their quiescent state in adult tissues. In several emergency situations related to organ damage, VSELs can be activated and mobilized into peripheral blood, and in appropriate animal models they contribute to tissue organ/regeneration. Interestingly, their number correlates with lifespan in mice, and they may also be involved in some malignancies. VSELs have been successfully isolated in several laboratories; however, some investigators experience problems with their isolation

Photoemission study of Pt/SrTiO3 interfaces

Tytanian strontu jest intensywnie badanym tlenkiem ze względu na jego potencjalne zastosowanie w przemyśle elektronicznym. W praktycznym wykorzystaniu potrzebne są elektrody, odbierające sygnał niesiony przez materiał. Dlatego też istotne jest pytanie o stabilność warstw powierzchniowych tytanianu strontu, gdy nakładane są na niego warstwy metalu. W niniejszym artykule prezentowane są wyniki badań fotoemisyjnych (spektroskopia fotoelektronów wzbudzanych promieniowaniem rentgenowskim XPS) na złączach Pt/SrTiO3. Złącza zostały wykonane poprzez naniesienie platyny na monokryształy SrTiO3 przez naparowanie lub napylenie. Prezentowane rezultaty wskazują, że obie metody depozycji powodują zmiany chemiczne w obszarze przypowierzchniowym badanych kryształów i zmiany te są intensywniejsze w przypadku napylania niż naparowywania. Dodatkowo przedyskutowano problem obecności wiązań chemicznych pomiędzy platyną a substratem. Nie stwierdzono obecności wiązań chemicznych w przypadku złącza z naparowaną warstwą metalu, natomiast prawdopodobny jest udział wiązania metalicznego w złączu z napyloną elektrodą.SrTiO3 is intensively investigated material with respect to potential applications in modern electronics technology. In practically used devices metallic electrodes are needed to control the information carrying oxide material. Than one of the questions related with mentioned applications of SrTiO3 is its surface layers chemical stability during metal deposition. In this work we shows results of X-ray Photoelectron Spectroscopy (XPS) investigations of Pt/SrTiO3 interfaces. Interfaces were prepared using two methods of platinum deposition on SrTiO3 single crystal: thermal evaporation and sputtering. This studies indicates that both methods lead to chemical instability of the crystal surface, however the changes are more pronounced in the case of sputtering technique. Additionally the problem of chemical bonding between Pt and the substrate was discussed. No indication of chemical bonds was found for the junction with evaporated Pt layer but metallic bond along the system with sputtered electrode can not be excluded

Low temperature reduction in Ta–O and Nb–O thin films

The effect of thermal reduction in ultra-high vacuum was studied in films of tantalum and niobium oxides obtained by oxidation of deposited metallic layers. The obtained films appeared to be amorphous and their stoichiometry was not uniform. For the Ta based film the main component was Ta2O5 while for the oxidized Nb film the pentoxide was present in the topmost part of the film and the thickest layer had the electron density assigned to NbO2. Thermal reduction was studied with the use of in situ photoelectron spectroscopy which revealed for the Nb–O film a strong effect for temperature as low as 300 °C. The Nb–O film reduced at 600 °C exhibited dominating metallic-like electronic states assigned to NbO. For the Ta–O film the significant reduction process started above 600 °C. At 900 °C the film showed metallic-like states which can be attributed to Ta2O. A single crystal of Nb2O5 showed no effect of reduction for temperatures up to 500 °C. A test performed with the use of local conductivity atomic force microscopy showed the most interesting bipolar-like resistive switching properties for the films reduced at temperatures up to 300 °C